There is known a post-processing apparatus for executing a post-processing on a sheet conveyed from an image forming apparatus (e.g., an MFP). The post-processing apparatus includes a processing section executing a stapling processing or a sorting processing on the conveyed sheet. In addition, the post-processing apparatus includes a saddle folding unit for executing saddle folding, i.e., folding a bundle of a plurality of sheets in half. A sheet is conveyed from the image forming apparatus via a sheet path to the saddle folding unit. The sheet conveyed to the saddle folding unit is accepted by a stacker. For example, the stacker accepts the conveyed sheet through a standing posture. A stapling unit for executing the stapling processing on the sheet is arranged above the stacker.
However, if the stapling unit knocks a staple in the sheet, there is possibility of causing deflection in the sheet in a sheet width direction. If the deflection in the sheet is caused, there is a likely possibility that a position of the staple in the sheet is deviated from the intended position to an unintended position.